Heat exchanger using an intermediate liquid



March 2, 1965 A. HUET HEAT EXCHANGER USING AN INTERMEDIATE LIQUID FiledJuly 3, 1962 IN VENTOR ANDRE HUET ATTORNEY United States Patent Ofiice3,171,477v Patented Mar. 2, 1965 3,171,477 HEAT EXCHAN GER USING ANINTERMEDIATE LIQUID Andre Huet, 48 Ave. du President Wilson, Paris,France Filed July 3, 1962, Ser. No. 207,276 Claims priority, applicationFrance, Sept. 18, 1961, 873,478 2 Claims. (Cl. 165106) For apparatusdesigned to produce an exchange of heat between two fluids there aregenerally used nests of tubes through the inside of which there flowsone of the fluids, while the other fluid flows over the outside thereof,the exchange of heat being effected through the wall of said tubes.

In the case of viscous fluids having a fouling action, such as thosewhich are encountered, for example, in the petroleum industry, thesefluids cause fouling or choking of the tubes of the exchanger at both oftheir faces and this results in a loss of exchange of heat and the needfor frequent cleaning operations interrupting the use of the apparatus.This cleaning is moreover practically impossible where the inside of thetubes is concerned.

The present invention has for its object a heat exchanger speciallydesigned for the exchange of heat between two viscous fluids having afouling action and in which an intermediate or secondary fluid, forexample water, circulating in closed circuit inside nests of tubes isused for transmitting the heat to be exchanged. These tubes are arrangedin such manner as to transfer the heat from one of the viscous fluidscirculating around a part of the nest of tubes containing theintermediate liquid to the other viscous fluid which it is desired toheat and which circulates around another part of the nest of tubes.

In its practical construction which forms the object of the presentinvention, the heat exchanger is constituted by half-casings, or smalltowers, which are superposed in pairs. Inside them are mounted andassembled, in closed circuit, from the lower half-casings to the upperhalf-casings, the nests of tubes containing the intermediate liquidsecuring the transfer of the heat. The viscous heating fluid circulatesaround the nests of tubes of the lower half-casings and the viscousfluid to be heated circulates around the nests of tubes of the upperhalf-casings. The circulation of the intermediate fluid, for examplewater, may be effected either by natural circulation or by forcedcirculation, the water circulating in the nest of tubes of the lowerhalf-casing being heated on contact with the viscous heating fluid, orbeing vaporised, and passing from there into the nest of tubes of theupper half-casing in which it is cooled or condensed, giving up its heatto the viscous liquid to be heated. It is possible to provide a largenumber of these half-casings operating in series, or in parallel, inorder to achieve all the heat exchange conditions which occur inpractice.

The nests of tubes may be produced with the aid of straight tubes or oftubes coiled in helices, which may be either of circular section or offlattened section of lenticular form, the arrangement of these tubesbeing devised so that the cleaning of their outer surfaces is easy andrapid.

The inside of the tubes of the nests containing the intermediate liquidis never fouled, since this is a liquid such as water, and the cleaningof the apparatus is confined to the outer surfaces of the nests oftubes.

The description which follows with reference to the accompanyingdrawings, which are given by way of example, will make it betterunderstood how the invention can be carried into effect.

FIG. 1 shows, in partially diagrammatic vertical section a first form ofembodiment of a unit forming the object of the invention.

FIG. 2 relates to a modified constructional form;

FIG. 3 shows diagrammatically the arrangement of a plurality of unitsthrough which the viscous fluids flow in parallel.

In the form of embodiment shown in FIG. 1, each heat-exchanger unit iscomposed of two identical jackets or casings a and b in the form of twosmall superposed columns or towers. Inside each of these columns a, bthere are disposed nests of tubes coiled in helices having as theircommon axis the axis XX of the columns. In the form of embodiment shown,there are three coils c, d, e of tubes in the form of helices throughwhich the intermediate or secondary fluid, which is water, flows inparallel. The tubes of the coils are either of circular section or, asshown in the drawing, of lenticular section, preferably with unequallyconvex faces. Three coaxial drums or cylinders c, d, 2, preferablyhaving their turns in contact, are thus formed.

In each of the columns a or b an axial header communicates through anexpansion turn g with a header h to which the circuits of the cylindersc, d, e are connected in parallel. The headers h are shown withhorizontal axes, but could have vertical axes. In the upper portion ofthe columns, the cylinders c, d, e open into a headeri which could havea vertical axis.

The intermediate or secondary fluid, for example water, flows throughthe cylinders c, d, e of the lower column, passes through the conduit jto the header 1' of the upper column a, where it flows through thecylinders c, d, e of the column a, and leaving through the lower header1 of the column a, returns through the conduit k to the lower header ofthe column b.

Through the column b flows the viscous fluid which is the heating fluid.This fluid arrives, in the direction of the arrow F, at the axial inlet1 at the top, flows through the column b from top to bottom and issuesin the direction of the arrow G at the bottom through the conduit m.

In the upper column a, the viscous fluid to be heated enters the inletorifice n at the bottom of the lower portion in the direction of thearrow H and issues, in the direction of the arrow I, at the top throughthe axial conduit 0.

The operation of the apparatus is as follows: the viscous heating fluidcirculating through the lower column b from F to G flows around thecylinders c, d, e and gives up its heat to the water circulating inthese cylinders, which is heated and vaporised. This water passesthrough the conduit j into the upper column a and circulates inside thecylinders c, a, e of this column, where it gives up its heat to theviscous fluid to be heated, which enters the column a at H and leaves itat I.

The water flows in closed circuit by natural circulation or else byforced circulation obtained by means of a pump p.

In order to procure the external cleaning of the circuits c, d, e of theupper column a, these circuits are preferably fast with the upper head qof the upper column a, which head is mounted removably. After theintermediate fluid circuit has been cut at r and s, it is possible towithdraw the complete nest of tubes 0, d, e from the casing a. In thecase of the lower column b, the assembly of circuits or cylinders c, d,e is fast with the lower head I and, after the intermediate fluidcircuit has been cut at u and y, the cylinders c, d, e are withdrawnfrom the column b at the bottom.

.and arranged in ring form around 'said' axis.

In the form of embodiment shown in FIG. 2, the general arrangement isthe same, but the tubes constituting the nests in which the intermediatefluid'circulat'es are rectilinear tubes parallel to the axis XX Thecirculation of intermediate fluid and the circulation of the viscousfluid are carried out as in the case of FIG. 1;

Likewise, the removal of the nests of tubes c, d, e toenable theirexternal surface to be cleaned is effected as in the case of FIG. 1.

Carrying into effect may comprise, asshown in FIG. 3,

the arrangement in parallel of a plurality of assemblies or unitssimilar to those which have just been described.

The viscous heating fluid circulates in parallel through the lowercolumns b, in the direction indicated by the arrows, if necessary underthe effect'of the'pump we The viscous fluid tobe heated circulates'inparallel through the upper columns a, in the direction indicated by thearrows, if necessary under the ettect of the pump w. Each pair ofcolumns a and b contain the nest of tubes in which flows theintermediate-fluid circulating in closed circuit as indicated in dashlines y in FIG. 3.

I claim: 7 p i 1. A heat exchanger apparatus for exchanging heat betweena secondary fluid and viscous fluids having fouling action comprising, alower, elongated, tubular casing and an upper elongated, tubular casingdisposed above the lower casing, a secondary closed circuit in operationfor containing therein in operation a secondary fluid comprising anupper and a lower heat transfer tube nest in each of saidcasingsrespectively extending longitu 4 secondary fluid flows in said lowertube nest generally upwardly and in said upper tube nest generally in anopposite downwardly direction, said lower casing having an upper inletand a lower outlet for flowing therethrough a viscous fluid in agenerally'counter-flow direction to the direction of flow of saidsecondary fluid for transferring heat therefrom to said secondary fluid,said'up'per casing having a lower inlet and'an upper outlet forvflowingthrough said lower 'casinga'viscous fluid in a generally counter-flowdirection'to'the "general direction of flow of'the secondaryfluidflowing through said upper tube nest thereby 'to extract heat fromsaid secondary fluid, said upper casing having an upper heat removabletherefrom, said upper tube nestbeing connected to said upper head forwithdrawal of the tube nest longitudinally fromthe'upper casing whensaid head is removed, a tubularfitting slidably mounted in a fluid-tightmanner extending through said-upper head and to whichsaid upper tubenest is connected and to which thefirst conduit means is connected, saidlower-casing having a removable lower head and means comprising anothertubular fitting extending through said lower head in a fluid-tightcondition for connecting-the lower tube nest to said lower head forwithdrawal of said lower tube nest longitudinally from said lower casingupon removal of said lower head. 7 a a 2. A heat exchanger apparatusaccording to claim 1,

inwhich each of said casings is internally free of baffles.

dinally therein, conduit means including a tubular fitting extendingthrough the top of said lower casing and slidably'rnounted therein in afluid-tight condition'connected for flowing secondary fluid from anupper end portion of said lower tube nest of each lower casing to anupper end portion'of said upper tube nest in said upper casing andconduit means including a tubular fitting extending through the, bottomof said upper casing and slidably mounted therein in a fluid-tightcondition connected for flowing secondary fluid from a lower end portionof said upper tube nest to a lower end portion of said lower tube vnestthereby to provide a flow path in which said References Cited by theExaminer W UNITED STATES PATENTS 2,595,195

5/52 Arbuckle 165108 2,911,199 1159 Huet 165177 FOREIGNPATENTS r1,175,619 11/58 France. j 1,224,106 2/60 France. 343,231 2/31 GreatBritain.

' 823,904 11/59 Great Britain.

1. A HEAT EXCHANGER APPARATUS FOR EXCHANGING HEAT BETWEEN A SECONDARYFLUID AND VISCOUS FLUIDS HAVING FOULING ACTION COMPRISING, A LOWER,ELONGATED, TUBULAR CASING AND AN UPPER ELONGATED, TUBULAR CASIG DISPOSEDABOVE THE LOWER CASING, A SECONDARY CLOSED CIRCUIT IN OPERATION FORCONTAINING THEREIN IN OPERATION A SECONDARY FLUID COMPRISING AN UPPERAND A LOWER HEAT TRANSFER TUBE NEST IN EACH OF SAID CASINGS RESPECTIVELYEXTENDING LONGITUDINALLY THEREIN, CONDUIT MEANS INCLUDING A TUBULARFITTING EXTENDING THROUGH THE TOP OF SAID LOWER CASING AND SLIDABLYMOUNTED THEREIN IN A FLUID-TIGHT CONDITION CONNECTED FOR FLOWINGSECONDARY FLUID FRON AN UPPER END PORTION OF SAID LOWER TUBE NEST OFEACH LOWER CASINGS TO AN UPPER END PORTION OF SAID UPPER TUBE NEST INSAID UPPER CASING AND CONDUIT MEANS INCLUDING A TUBULAR FITTINGEXTENDING THROUGH THE BOTTOM OF SAID UPPER CASING AND SLIDABLY MOUNTEEDTHEREIN IN A FLUID-TIGHT CONDITION CONNECTED FOR FLOWING SECONDARY FLUIDFROM A LOWER END PORTION OF SAID UPPER TUBE NEST TO A LOWER END PORTIONOF SAID LOWER TUBE NEST THEREBY TO PROVIDE A FLOW PATH IN WHICH SAIDSECONDARY FLUIDS FLOW IN SAID LOWER TUBES NEST GENERALLY UPWARDLY AND INSAID UPPER TUBE NEST GENERALLY IN AN OPPOSITE DOWNWARDLY DIRECTION, SAIDLOWER CASING HAVING AN UPPER INLET AND A LOWER OUTLET FOR FLOWINGTHERETHROUGH A VISCOUS FLUID IN A GENERALLY COUNTER-FLOW DIRECTION TOTHE DIRECTION OF FLOW OF SAID SECONDARY FLUID FOR TRANSFERRING HEATTHEREFROM TO SAID SECONDARY FLUID, SAID UPPER CASING HAVING A LOWERINLET AND AN UPPER OUTLET FOR FLOWING THROUGH SAID LOWER CASING AVISCOUS FLUID IN A GENERALLY COUNTER-FLOW DIRECTION TO THE GENERALDIRECTION OF FLOW OF THE SECONDARY FLUID FLOWING THROUGH SAID UPPER TUBENEST THEREBY TO EXTRACT HEAT FROM SAID SECONDARY FLUID, SAID UPPERCASING HAVING AN UPPER HEAT REMOVABLE